1. Field of the Invention
The present invention relates to an image display apparatus.
2. Description of the Related Art
Conventionally, image display apparatuses having a plurality of electron-emitting devices are known. The electron-emitting device includes a field-emission type electron-emitting device, a metal/insulator/metal type electron-emitting device, and a surface conduction electron-emitting device. The field-emission type electron-emitting device is electron-emitting device using a phenomenon that when a strong electric field which exceeds 107V/cm is generated on a surface of a solid such as metal or semiconductor in a vacuum, electrons are emitted from the solid into vacuum. Such phenomenon is caused by an increase in tunneling probability of electrons in the solid into vacuum because a vacuum level is distorted by the strong electric field. The tunneling probability of electrons in the solid into vacuum increases in an exponential manner with respect to the increase in the field strength.
The field-emission type electron-emitting device has an electrode (gate) which controls an electric field near a cathode (emitter) and a cathode surface. Since the field-emission type electron-emitting device can be miniaturized, various applications are expected. For example, the field-emission type electron-emitting device is used as an electron source, so as to be capable of being applied to the above-mentioned image display apparatuses.
Such image display apparatuses have a display panel, a driving circuit, a control circuit, a power source and a high-voltage power source.
Display panels generally have a rear plate and a face plate. The rear plate has a plurality of scanning wirings and a plurality of signal wirings arranged in a matrix, and a plurality of electron-emitting devices arranged respectively at intersection points of the scanning wirings and the signal wirings. The face plate is provided so as to be opposed to the rear plate, and has a light-emitting member which emits light due to electron collision. The face plate and the rear plate are fixed to an outer frame so that a vacuum is maintained therebetween. A getter which maintains vacuum is provided into a space surrounded by the face plate, the rear plate and the outer frame. A gap between the face plate and the rear plate is kept by a structure supporting member (spacer).
The driving circuit is a circuit which applies a voltage to the scanning wirings and the signal wirings. The control circuit is a circuit which controls the driving circuit. The power source is for supplying a power to the circuits. The high-voltage power source is for applying a high voltage to the face plate (for generating a strong electric field between the face plate and the rear plate).
The image display apparatus having the electron-emitting device is a “self light-emitting” display device in which a phosphor on the face plate emits light. For this reason, such image display apparatuses have a feature such that images whose contrast, color purity and realistic sensation are high can be displayed in bright and dark places.
In the image display apparatuses having the electron-emitting device, however, since the electron sources are independent according to pixels, image quality is deteriorated due to variation of characteristics of the electron sources in manufacturing and variation of fluctuation in characteristics caused by long-time operation (display of images).
A conventional technique from a viewpoint of such a problem is disclosed in Japanese Patent Application Laid-Open No. 2001-209352. An image display apparatus disclosed in Japanese Patent Application Laid-Open No. 2001-209352 has an ampere meter which detects an amount of current flowing in a high-voltage power source. The image display apparatus disclosed in Japanese Patent Application Laid-Open No. 2001-209352 stores an amount of the current flowing in the high-voltage power source into the memory in synchronization with timing (timing pulse) at which a driving circuit applies a voltage, and corrects a voltage to be applied to the electron-emitting devices (electron sources) based on the stored amount of the current.